Ruler of the Rock Day is a special occasion featured in the Fraggle Rock episode "The Finger of Light." On this day, which occurs when decreed by the World's Oldest Fraggle, Fraggles may participate in a game to become Ruler of the Rock (for a limited time only).

Normally involving five participants (though four have been allowed), the players must travel across The Echo Hole to a cave to await The Finger of Light. Whomever the light shines upon will become Ruler of the Rock and is allowed three commands before their reign is over.